Abstract
“...an eerie type of chaos can lurk just behind a facade of order, and yet deep inside the chaos lurks an even eerier type of order.” Douglas Hofstadter
Bypass transition to turbulence in boundary layers is examined using linear theory and direct numerical simulations (DNS). First, the penetration of low-frequency free-stream disturbances into the boundary layer is explained using a model problem with two time scales, namely the shear and wall-normal diffusion. The simple model provides a physical understanding of the phenomenon of shear sheltering. The second stage in bypass transition is the amplification of streaks. Streak detection and tracking algorithms were applied to examine the characteristics of the streak population inside the boundary layer, beneath free-stream turbulence. It is demonstrated that simple statistical averaging masks the wealth of streak amplitudes in transitional flows, and in particular the high-amplitude, relatively rare events that precede the onset of turbulence. The third stage of the transition process, namely the secondary instability of streaks, is examined using secondary instability analysis. It is demonstrated that two types of instability are possible: An outer instability arises near the edge of the boundary layer on the lifted, low-speed streaks. An inner instability also exists, and has the appearance of a near-wall wavepacket. The stability theory is robust, and can predict the particular streaks which are likely to undergo secondary instability and break down in transitional boundary layers beneath free-stream turbulence. Beyond the secondary instability, turbulent spots are tracked in DNS in order to examine their characteristics in the subsequent non-linear stages of transition. At every stage, we compare the findings from linear theory to the empirical observations from direct solutions of the Navier-Stokes equations. The complementarity between the theoretical predictions and the computational experiments is highlighted, and it leads to a detailed view of the mechanics of transition.
Similar content being viewed by others
References
Andersson, P., Berggren, M., Henningson, D.S.: Optimal disturbances and bypass transition in boundary layers. Phys. Fluids 11(1), 134–150 (1999)
Andersson, P., Brandt, L., Bottaro, A., Henningson, D.S.: On the breakdown of boundary layer streaks. J. Fluid Mech. 428, 29–60 (2001)
Barkley, D., Blackburn, H.M., Sherwin, S.J.: Direct optimal growth analysis for time steppers. Int. J. Num. Meth. Fluids 57, 1435–1458 (2008)
Brandt, L., Schlatter P., Henningson, D.S.: Transition in boundary layers subject to free-stream turbulence. J. Fluid Mech. 517, 167–198 (2004)
Brandt, L., de Lange, H.C.: Streak interactions and breakdown in boundary layer flows. Phys. Fluids 20, 024107 (2008)
Butler, K.M., Farrell, B.F.: Three-dimensional optimal disturbances in viscous shear flow. Phys. Fluids A 4, 1637–1650 (1992)
Cantwell, B., Coles, D., Dimotakis, P.: Structure and entrainment in the plane of symmetry of a turbulent spot. J. Fluid Mech. 87(04), 641–672 (1978)
Durbin, P.A., Zaki, T.A., Liu, Y.: Interaction of discrete and continuous boundary layer modes to cause transition. Int. J. Heat Fluid Flow 30, 403–410 (2009)
Durbin, P., Wu, X.: Transition Beneath Vortical Disturbances. Ann. Rev. Fluid Mech. 39, 107–128 (2007)
Emmons, H.W.: The laminar-turbulent transition in a boundary layer. Part i. J. Aero. Sci. 18, 490–498 (1951)
Fasel, H.F.: Numerical investigation of the interaction of the Klebanoff-mode with a Tollmien–Schlichting wave. J. Fluid Mech. 450, 1–33 (2002)
Goldstein, M.E., Wundrow, D.W.: On the environmental realizability of algebraically growing disturbances and their relation to Klebanoff modes. Theor. Comput. Fluid Dyn. 10, 171–186 (1998)
Görtler, H.: Instabilität laminarer Grenzschichten an konkaven Wänden gegenüber gewissen dreidimensionalen Störungen. Z. Angew. Math. Mech. 21, 250–252 (1941)
Grosch, C.E., Salwen, H.: The stability of steady and time-dependent plane Poiseuille flow. J. Fluid Mech. 34, 177–205 (1968)
Grosch, C.E., Salwen, H.: The continuous spectrum of the Orr–Sommerfeld equation. Part 1. The spectrum and the eigenfunctions. J. Fluid Mech. 68, 33–54 (1978)
Hack, M.J.P., Zaki, T.A.: The continuous spectrum of time-harmonic shear layers. Phys. Fluids 24, 034101 (2012)
Hack, M.J.P., Zaki, T.A.: Streak instabilities in boundary layers beneath free-stream turbulence. J. Fluid Mech. (2013, under review)
Hultgren, L.S., Gustavsson, L.H.: Algebraic growth of disturbances in a laminar boundary layer. Phys. Fluids 24, 1000–1004 (1981)
Hunt, J.C.R., Durbin, P.A.: Perturbed shear layers. Fluid Dyn. Res. 24, 375–404 (1999)
Jacobs, R.G., Durbin, P.A.: Shear sheltering and the continuous spectrum of the Orr-Sommerfeld equation. Phys. Fluids 10, 2006–2011 (1998)
Jacobs, R.G., Durbin, P.A.: Simulations of bypass transition. J. Fluid Mech. 428, 185–212 (2001)
Kleiser, L., Zang, T.A.: Numerical simulation of transition in wall-bounded shear flows. Ann. Rev. Fluid Mech. 23, 495–537 (1991)
Landahl, M.T.: A note on an algebraic instability of inviscid parallel shear flows. J. Fluid Mech. 98, 243–251 (1980)
Leib, S.J., Wundrow, W., Goldstein, M.e.: Effect of free-stream turbulence and other vortical disturbances on a laminar boundary layer. J. Fluid Mech. 380, 169–203 (1999)
Liu, Y., Zaki, T.A., Durbin, P.A.: Boundary layer transition by interaction of discrete and continuous modes. J. Fluid Mech. 604, 199–233 (2008)
Liu, Y., Zaki, T.A., Durbin, P.A.: Floquet analysis of secondary instability of boundary layers distorted by Klebanoff streaks and Tollmien–Schlichting waves. Phys. Fluids 20, 124102 (2008)
Luchini, P.: Reynolds-number-independent instability of the boundary layer over a flat surface: optimal perturbations. J. Fluid Mech. 404, 289–309 (2000)
Mandal, A.C., Venkatakrishnan, L., Key, J.: A study on boundary-layer transition induced by free-stream turbulence. J. Fluid Mech. 660, 114–146 (2010)
Matsubara, M., Alfredsson, P.: Disturbance growth in boundary layers subjected to free-stream turbulence. J. Fluid Mech. 430, 149–168 (2001)
Nagarajan, S., Lele, S. K., Ferziger, J. H.: Leading-edge effects in bypass transition. J. Fluid Mech. 572, 471–504 (2007)
Nolan, K., Walsh, E.J.: Particle image velocimetry measurements of a transitional boundary layer under free stream turbulence. J. Fluid Mech. 702, 215–238 (2012)
Nolan, K., Zaki, T.A.: Conditional sampling of transitional boundary layers in pressure gradients. J. Fluid Mech. 728, 306–339 (2013)
Ovchinnikov, V., Choudhari, M.M., Piomelli, U.: Numerical simulations of boundary-layer bypass transition due to high-amplitude free-stream turbulence. J. Fluid Mech. 613, 135–169 (2008)
Phillips, O.M.: Shear-flow turbulence. Ann. Rev. Fluid Mech. 1, 245–264 (1969)
Rosenfeld, M., Kwak D., Vinokur M.: A fractional step solution method for the unsteady incompressible Navier-Stokes equations in generalized coordinate systems. J. Comput. Phys. 94, 102–137 (1991)
Saric, W.S., Reed, H.L., White, E.B.: Stability and transition of three-dimensional boundary layers. Ann. Rev. Fluid Mech. 35, 413–440 (2003)
Schlatter, P., Brandt, L., de Lange, H.C., Henningson, D.A.: On streak breakdown in bypass transition. Phys. Fluids 20, 101505 (2008)
Schrader, L.-U., Brandt, L., Zaki, T.A.: Receptivity, instability and breakdown of Görtler flow. J. Fluid Mech. 682, 362–396 (2011)
Swearingen, J.D., Blackwelder, R.F.: The growth and breakdown of streamwise vortices in the presence of a wall. J. Fluid Mech. 182, 255–290 (1987)
Vaughan, N.J., Zaki, T.A.: Stability of zero-pressure-gradient boundary layer distorted by unsteady Klebanoff streaks. J. Fluid Mech. 681, 116–153 (2011)
Westin, K.J.A., Boiko, A.V., Klingmann, B.G.B., Kozlov, V.V., Alfredsson, P.H.: Experiments in a boundary layer subjected to freestream turbulence. Part I: boundary layer structure and receptivity. J. Fluid Mech. 281, 193–218 (1994)
Wu, X., Durbin, P.A.: Evidence of longitudinal vortices evolved from distorted wakes in a turbine passage. J. Fluid Mech. 446, 199–228 (2001)
Zaki, T.A., Durbin, P.A.: Mode interaction and the bypass route to transition. J. Fluid Mech. 531, 85–111 (2005)
Zaki, T.A., Durbin, P.A.: Continuous mode transition and the effects of pressure gradient. J. Fluid Mech. 563, 357–388 (2006)
Zaki, T.A., Saha, S.: On shear sheltering and the structure of vortical modes in single and two-fluid boundary layers. J. Fluid Mech. 626, 111–148 (2009)
Zaki, T.A., Wissink, J.G., Durbin, P.A., Rodi, W.: Direct computations of boundary layers distorted by migrating wakes in a linear compressor cascade. Flow, Turb. & Comb. 83, 307–322 (2009)
Zaki, T.A., Wissink, J.G., Rodi, W., Durbin, P.A.: Direct numerical simulations of transition in a compressor cascade: the influence of free-stream turbulence. J. Fluid Mech. 665, 57–98 (2010)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Zaki, T.A. From Streaks to Spots and on to Turbulence: Exploring the Dynamics of Boundary Layer Transition. Flow Turbulence Combust 91, 451–473 (2013). https://doi.org/10.1007/s10494-013-9502-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10494-013-9502-8